yes thats the stuff. read this article, it will set you off on the right track.
http://www.reefkeeping.com/issues/2006-02/rhf/index.php
then use this calculator to figure out how much you need.
http://reef.diesyst.com/flashcalc/flashcalc.html
what do you have in your tank for corals, lighting, etc?
any questions just feel free to ask here.